Each link of pintle chain includes a barrel which connects the sidebars at the closed end of the link. The side bars are offset outwardly at the open end of the link and are fitted with a connecting pin to extend through and turn in the bore of the barrel of the next adjacent link. In a conveyor chain, for example, where the chain is under maximum tension in approaching the drive sprocket and is otherwise under less or nominal tension, pintle chain is operated with its open end forward. The advantage here is in that the pin of the link engaging the sprocket under tension turns in the barrel of the next preceding link and the barrel of the link only turns relative to the sprocket while disengaging the sprocket and only while under relatively less or nominal tension. This is well understood. It is somewhat less well understood that no such advantage is obtained in the use of pintle chain operating in either direction and/or between drive and driven sprockets of similar diameters.
The object of the present invention is to extend the wear life and servicability of a pintle chain and its drive sprocket. Applications which include a driven sprocket, as such, are excluded here. However, the chain of the present invention can operate over guide or return sprockets which do not require any significant force to effect their turning. Applications where the chain leaving the drive sprocket is under significant tension, are also excluded here. The present invention has the following enumerated advantages:
(1) The unique shape extends the life of chain by placing material at those areas on the barrel (or bushing) where wear is known to occur.
(2) The unique shape reduces the stress at the interface between the chain and the sprocket from "line" pressure to "area" pressure, which reduces the wear.
(3) The shape approximates that of the sprocket tooth which distributes the chain load over a wide area of the sprocket, reducing sprocket tooth wear.
(4) The area in contact with the bottom diameter allows for reduced pressure and less wear from movement of chain through the pitch line clearance of the sprocket as each chain link rotates on the sprocket.
(5) If the chain were to move out of the tooth pocket, to accomodate chain elongation then this unique shape will allow for more chain elongation before the chain malfunctions.
(6) A more economical base material is made possible, like nonmetallics of acetal resin or nylon resin et al., because of the favorable distribution of the chain load on the sprocket.
(7) A symmetrical-shaped bushing allows for added chain life since the chain can be "turned over. "
(8) More barrel area is required to assure turning of some idler wheels which is accomplished by this shaped barrel.